Diagnostic usefulness of FDG-PET for malignant somatostatinoma of the pancreas.

A 24-year-old female complaining of diarrhea and back pain was admitted to hospital where a tumor of the pancreatic head was revealed on a computed tomography (CT) scan. Abdominal ultrasonography, CT and celiac angiography revealed a hypervascular lesion on the pancreas. An endocrine tumor, particularly a somatostatinoma, was suspected and hormone levels in the blood were examined. Serum hormone levels were normal, so FDG-PET was performed. An abnormally high accumulation of FDG was detected on the FDG-PET image at the head of the pancreas, and the SUV of the lesion was 3.2, so the mass was considered to be malignant on FDG-PET. Pylorus-preserving pancreatoduodenectomy was performed with a preoperative diagnosis of malignant endocrine tumor. The resected specimen revealed a massive, yellowish-white tumor of the pancreas head measuring 50x 45x38mm. Histologically, the tumor was a malignant islet-cell tumor, and immunohistochemically the tumor stained with an anti-somatostatin antibody, but not with antibodies against glucagons, insulin or vasoactive intestinal polypeptide. The patient was discharged after the operation and has remained well without recurrence for 5 years. Liver metastatic tumors, however, appeared 6 years after the operation.